"We can't keep our arms crossed in front of a real overweight and obesity epidemic. The lives of millions of Mexicans are literally at risk," Pena Nieto said.
Seven in 10 adults are either overweight or obese in Mexico, while one-third of the country's children fall in that category, according to official figures.
Mexico now has a higher rate of overweight people than the United States, and it also has the highest prevalence of diabetes among the 34-nation Organisation of Economic Co-operation and Development.
Presenting his national strategy to prevent obesity and diabetes, Pena Nieto said the health ministry will open an "observatory" to monitor and respond to the problem.
The strategy includes a campaign to promote healthier lifestyles and better diets in a country that consumes 163 liters (43 gallons) of sugary drinks per capita per year, the highest rate in the world.
The Mexican leader also cited special taxes that the Congress is about to pass on sodas and junk food, saying the funds should be used for health programs and to increase access to drinking water in schools.
Pena Nieto also called for a "change of attitude and culture" in Mexico.
Citing a health activist, Pena Nieto urged his countrymen to "dedicate at least one hour per day to exercise or a physical activity, which doesn't require much effort but that breaks with sedentary lifestyles... be it walking, climbing stairs."